Rights management (RM) and enforcement is highly desirable in connection with digital content such as digital audio, digital video, digital text, digital data, digital multimedia, etc., where such digital content is to be distributed to one or more users. Digital content could be static, such as a text document, for example, or it could be streamed, such as the streamed audio and video of a multimedia presentation. Typical modes of distribution of such streamed content include tangible and intangible forms such as an optical disk, a cable-access feed, a feed from an electronic network such as the Internet, a feed from an over-the-air broadcast, etc. Upon being received by a user at an appropriate computing device thereof, such user renders the streamed digital content with the aid of the computing device, appropriate rendering software, and appropriate output devices such as speakers, a video monitor, etc.
In one scenario, the streamed content is distributed by a distributor as part of a subscription service, such as for example a digital television service, and the streamed content as distributed is either protected, such as for example by being encrypted, or is unprotected. If it is the case that the streamed content is indeed distributed in an unprotected form, it may be the case that the distributor primarily intends for the streamed content to be immediately consumed and rendered, and not stored in any meaningful retrievable form. For example, the streamed content may be one of many streams of content in a digital cable television signal that is to be received by a digital cable set-top box and immediately rendered thereby, and is then to be forwarded to the aforementioned appropriate output devices.
However, it is to be appreciated that storage systems exist and/or are being developed that can indeed store the streamed content for later rendering and/or re-distribution to other computing devices. With regard to such storage systems, then, the distributor of the streamed unprotected content would rather not have such unprotected content stored in the unprotected form and without any ability to restrict such re-distribution, if so desired. In particular, the distributor or the like may wish to prohibit the user from copying such streamed content to another storage system or the like, may wish to allow the user to copy with temporal and/or count restrictions, or the like. As may be appreciated, by prohibiting unlimited copying of the streamed content, the distributor can avoid the unchecked dispersal of pristine digital copies of the streamed content, where such unchecked dispersal would encourage other users from foregoing from subscribing to the subscription service offered by such distributor.
In addition, the distributor may wish to provide various users with different rendering rights. For example, the distributor may offer different tiers of service, where higher-level tiers correspondingly command higher subscription fees, and where a user subscribing at a particular tier should not be allowed to access streamed content from higher tiers in an unprotected form.
Note, though, that after the streamed content has been distributed, the distributor has very little if any real control over the streamed content. This is especially problematic in view of the fact that most any personal computer includes the software and hardware necessary to make an exact digital copy of such streamed content, and to download such exact digital copy to a re-distribution medium such as an optical disk, or to send such exact digital copy over a network such as the Internet to any destination.
Of course, as part of a transaction wherein the streamed content is subscribed to, the distributor may require the user/recipient of the streamed content to promise not to re-distribute such content in an unwelcome manner. However, such a promise is easily made and easily broken. The distributor may attempt to prevent such re-distribution through any of several known security devices, usually involving encryption and decryption. However, such security devices if especially simple pose little problem to a mildly determined user who wishes to decrypt encrypted content, save such content in an un-encrypted form, and then re-distribute same.
RM and enforcement architectures and methods have thus been provided to allow the controlled rendering of arbitrary forms of digital content including streamed content, where such control is flexible and definable by the distributor or the like of such digital content. Such architectures allow and facilitate such controlled rendering in the scenario as set forth above.
In one particular arrangement, the streamed content is one of a plurality of streams of such content provided as a combined signal to a receiver. The receiver selects a particular one of the streams upon command from a media system, and provides the selected stream to such media system for further processing. Notably, the selected stream as provided to the receiver is unprotected, but prior to being provided to the media system the selected stream is in fact protected by the receiver according to a particular RM encryption system.
Typically, in an RM encryption system, the content is protected by being encrypted according to a content key (CK). Inasmuch as symmetric encryption and decryption is easier, faster, and less expensive than asymmetric encryption and decryption, such content key (CK) is typically symmetric. Also typically, the content key (CK) is provided by an encryptor such as the receiver to a decryptor such as the media system in an encrypted form and as part of a digital license or the like that specifies license rules that must be satisfied before such content is allowed to be decrypted and rendered by the decryptor/media system.
In the circumstance where the streamed content is one of a plurality of digital television signals that may in effect be tuned by the receiver at the command of the media system, it is to be appreciated that the receiver can be expected to receive commands from the media system to tune in different digital signals on a fairly regular basis, perhaps on the order of as much as once every one-half to one second, especially if the user of the media system is in effect skimming through or ‘surfing’ several signals. However, and recognizing that each newly tuned signal requires a new license from the receiver, it is to be appreciated that constructing such new license and sending same from the receiver to the media system can be quite burdensome, especially if the license is detailed, includes encrypted elements, includes a digital signature, or the like. Thus, it likely cannot be expected that the receiver completely creates a new license every time the media system commands such receiver to tune a different digital signal, especially if the frequency of such commands is on the order of seconds.
A need exists then, for a system and method for the receiver to create a shortened version of requirements that would go into such a new license such that the receiver need not go to the burden of in fact completely creating such new license every time such receiver newly tunes a digital signal. In particular, a need exists for such a shortened version of such requirements that can be quickly created and sent to the media system each time the receiver newly tunes a digital signal, even if the user is commanding a change on the order of once every second or so. Additionally, a need exists for such a shortened version of such requirements that is concise and yet describes all license requirements for the tuned digital signal in a minimal amount of space. Finally, a need exists for such a shortened version of such requirements that can be employed in connection with streamed digital content as provided to the media system from sources other than the receiver.
Also recognizing that each newly tuned signal may be encrypted by the receiver according to a different content key (CK), it is to be appreciated that informing the media system of such content key (CK) by placing same in a new license and sending same from the receiver to the media system can likewise be quite burdensome. Again, it likely cannot be expected that the receiver completely creates a new license with a new content key (CK) every time the media system commands such receiver to tune a different digital signal, especially if the frequency of such commands is on the order of seconds.
A need exists then, for a system and method for sharing each new content key (CK) between the receiver and the media system without the need for creating an actual license with each such content key (CK) therein. In particular, a need exists for a method by which the receiver and media system can exchange an initial content key and then rotate content keys based on the initial content key. Additionally, a need exists for such a method whereby the receiver and the media system rotate keys in a coordinated fashion.
Further recognizing that the requirements corresponding to a newly tuned signal may be located within the signal on a periodic basis, but that such periodicity may be a relatively long period of time, it is to be appreciated that it may be unreasonable to make the media system wait such a relatively long period of time until such requirements are in fact located within such signal. Especially in the situation where the receiver is tuning in different digital signals on a fairly regular basis, perhaps on the order of as much as once every one-half to one second, it likely cannot be expected that the receiver can wait the relatively long period of time to locate the requirements within the newly tuned signal.
A need exists then, for a system and method for the receiver to send a default set of requirements on a preliminary basis, and then an actual set of requirements when actually located. In particular, a need exists for a method by which the receiver can send such default requirements to be employed by the media system until the actual requirements are sent. Additionally, a need exists for such a method whereby the media system can distinguish between such default requirements and such corresponding actual requirements and can replace the default requirements with the corresponding actual requirements upon receipt thereof.
Finally recognizing that the media system likely will store a relatively large amount of licenses corresponding to newly tuned signals, but that many if not most of such licenses are not needed for very long, it is to be appreciated that such licenses should for the most part be stored on only a temporary basis. Once again, in the situation where the receiver is tuning in different digital signals on a fairly regular basis, perhaps on the order of as much as once every one-half to one second, it likely cannot be expected that all of the corresponding licenses as created and stored by the media system should or could be made available on a permanent basis.
A need exists then, for a system and method for the media system to store at least some licenses corresponding to tuned signals only on a temporary basis. In particular, a need exists for a method by which the media system can recognize which licenses need only be stored on a temporary basis. Additionally, a need exists for such a method whereby the media system deletes such temporarily stored licenses.